Controlling temperature in exothermic reactions



April 18, 1939. J; E. WESTENBERG 4,

CONTROLLING TEMPERATURE IN,EXOTHERMIC REQAQTIONS I Filed June 15, 19382s STABILIZER REACTORS HEAT EXCHANGER TEMPERATURE INVENTOR JOSEPH E.WESTE INBERG' ATTORNEY Patented A r. 18,1939

UNITED STATES PATENT OFFlCE CONTROLLING TEMPERATURE IN EXO- THERMICREACTIONS 10 Claims. (Cl. 196-10) The invention particularly relates toa novel and advantageous method and means of definitely controlling thetemperature of a stream of reactants being supplied to a reaction zoneand 5 definitely controlling the temperature of the products leavingsaid reaction zone.

In most of the numerous varities of exothermic reactions it is necessaryto supply the charging stock to the reaction zone at a fairly constant10 predetermined temperature. This temperature should be suificientlyhigh to' indicate the desired reaction and sufficiently low to precludean excessive temperature rise in the reaction zone and thereby precludeor minimize the formation 15 of undesired products. In most cases thetemperature to which the resulting reaction products are raised by theheat evolved in the exo-' thermic reaction exceeds that required fortheir subsequent treatment and it is desirable to recover the excessheat for use in other portions of the system where heat is: required. Itis, of

course an old expedient to pass the charging stock and, at the sametime, preheat the charging stock to the specific temperature required.

30 Theinvention accomplishes the object of heating the charging stock tothe desired temperature and cooling the reaction products to the desiredtemperature by employing two heat exchange steps operated in parallelarrangement.

35 A regulated portion of the total stream of charging stock is passedin indirect heat exchange with the reaction products, the remainingportion passed in indirect heat exchange with an independent heatingmedium and the separately heated portions are thence commingled andsupplied to the reaction zone. The quantity of charging stock passed inindirect heat exchange with the reaction products is regulated to coolthe. latter to the desirediemperature' and the temperature to which theremainder of said charging stock is heatedin the other heat exchangestep'is controlled to produce the desired temperature in thetotaL-charging stock entering the reaction zone upon commingling thepre--,

55 the charging stock and cool the reaction products and wherein thereaction products do not contain sufficient excess heat to bring thecharging stock to the desired temperature by indirect heat exchangetherewith. It is therefore apparent that the adaptability of theinvention is 5 not limitedto exothermic reactions but that it may alsobe utilized to advantage in many endothermic reactions wherein thetemperature level and quantity of the products leaving the reaction zoneis not sufficient to preheat the total charging stock to the desiredtemperature.

Although, as above stated, the invention is adapted to be used inconjunction with either endothermic or exothermic reactions, it isparticularly advantageous as applied to exothermic reaction systemswherein the reaction zone is not controllably cooled and to endothermicreaction systems wherein it is desired to limit direct external'heatingof the reaction zone.

One specific embodiment of the invention involves its use inconjunction'with a system for the catalytic polymerization of normallygaseous olefins, such as propene and/or butenes, to produce liquidproducts of high antiknook value boiling within the range of gasoline. Adescription of this type of system and the manner in which the featuresof the invention may be applied thereto will be used to illustrate theprocess of the invention .in conjunction with the accompanying drawing,but this illustration is not to be construed as a limitation. g

The drawing diagrammatically illustrates a catalytic polymerizationapparatus of the type above mentioned in which the features of theinvention have been incorporated.

Referring to the drawing, the charging stock, which in this caseconsists of a mixture of olefinic and paraffinic gases containing asubstantial quantity of readily polymerizable olefins,'is supplied fromany suitable source such as, for ex- 40 ample, the stabilizer or othergas separating or concentrating equipment of a cracking system,

-not illustrated, through line I and valve 2.- A

of the charging stock is directed from line I through line 5 to heatexchanger 6 wherein its temperature is increased to the desired degreeby indirect heat exchange in this zone with a suitable heating mediumsupplied thereto through line I and control valve 8 and dischargedtherefrom through line 9.

The stream of charging stock preheated in heat exchanger 8 is directedtherefrom through line I and commingles in line I! with the stream ofcharging stock preheated in heat exchanger 4 and directed therefrom toline If through line H.

The resulting commingled stream of preheated charging stock passesthrough line I! to reactor l3 and the'resulting reaction products passfromreactor I! through line l4 and valve ii to reactor l8.

Reactors l3 and I8, in this particular case, are I similar reactionzones, each containing. a bed of suitable catalytic material such as,for example, what is now known in the art as solid phosphoric acidcatalys One or any desired number of such reactors may, of course, beemployed in series or in parallel arrangement within the scope of theinvention. The use of such reactors, the

. method of supporting a catalyst bed and the type of catalyst suitablefor polymerization of the oleflnic components of the charging stock,such of high antiknock value boilingwithin the range of gasoline,are-now well known in the art and do not require illustration ordetailed description.

The stream of normally liquid polymers and unconverted components of thegaseous mixture supplied to the system as charging stock are directedfrom reactor It in relatively hot vaporous state through line ii to heatexchanger 4 wherein they are cooled to the desired temperature byindirect heat exchange with that portion of the charging stock supplied,as previously described,

as propene and/or butenes, to produce materials to this zone. Theresulting partially cooled conv the lower portion of the stabilizer forreboiling.

the polymer gasoline by passing a suitable heatv version products aredirected from heat exchanger 4 through line l8 and the valve l9 tostabilizer 28. Valve I9 is provided, in this particular case, for thepurpose of reducing the pressure employed in stabilizer 28 relative tothat utilized in the reaction zone, although this is not an essentialrequirement of the process.

- The purpose of stabilizer 28 is to liberate from the polymer gasolineregulated quantities of dissolved normally gaseous components andthereby reduce its vapor pressure to the desired degree. This type oftreatment is well known and stabilizer 28 may be of any conventionalform. In the case here illustrated, heat is supplied to ing mediumthrough closed coil 2!. Controlled cooling in the upper portion of thestabilizer is accomplished, in the case here illustrated, by passingasuitable cooling medium through closed coil 22. Other conventionalreboiling and/or cooling means may, of course, be substituted 'whendesired. Stabilized polymer gasoline of the desired vapor pressure iswithdrawn from the lower portion of stabilizer 28 and directed throughline 28 and valve 24 to-cooling and temperature of the conversionproducts passed through heat exchanger 4 to the desired degree.

This temperature is preferably such that 'the stream of conversionproducts entering stabilizer 20 is in partially vaporous and partiallyliquid state, the additional heat required for the desired stabilizationbeing accomplished by reboiiing of the stabilizer bottoms either withinor external to the stabilizer. When stabilizer 28 is operated at a lowerpressure than that employed in heat exchanger 4, the pressure reductionwill, of course, accomplish some cooling of the conversion products andaccount must be taken of this cooling eflect in controlling thetemperature of the conversion products leaving heat exchanger 4.Preferably, in such-casearthe temperature is measured on the lowpressure side of valve I8 and valve 3 is adjusted in accordance with thetemperature to admit only the required amount of charging stock to heatexchanger 4.

The quantity of heat supplied to heat exchanger 6 to that portion of thecharging stock passed through'this zone isdetermined by the ftemperature of the commingled streams of preheated charging stockpassing through line I2,

so that the temperature of the charging stock entering the reaction zoneis maintained substantially constant. This is accomplished, in the casehereilustrated, by measuring the temperature of the stream of preheatedcharging stool: passing through line I! and accordingly adjusting valve8 in line l'to permit the admission of only the required'amount ofheating medium to heat exchanger 8.

It will be apparent from the above that by proper regulation of valves 3and 8 the temperature of the charging stock entering the reaction zoneand the temperature of the reaction products-entering stabilizer mayboth be deflnitely controlled within narrow limits. This may beaccomplished by the manual adjustment of valves 3 and 8, the adjustmentof valve lbeing determined by the temperature of the commingled streamsof charging stock passing through line I2 and the adjustment of valve 8being determined by the temperature. of the reaction products enteringstabilizer .20. Conventional automatic control equipment may, however,be

. employed to accomplish the adjustment of valve 3 in response to minorvariations in the temperature of the commingled streams of preheatedcharging stock in line, l2 and to accomplish the adjustment of valve 8in response to minor variations in the temperature of the reactionprod-'- ucts entering the stabilizer. Such controllers are nected with asuitable temperature-sensitive device in line H and with valve 8 in sucha manner that the contour functions to adjust the opening through thevalve in inverse relation to variations-in the temperature of the streampassing through line l2. Controller 28 is connected with line l8andvalve 3 and functionsto adjust the opening through thev'alve indirectrelation to temperature variationsin line I2.

indicated at 21 and 28. Controller .21 is con- 7 Other suitablecontrollers, not illustrated, may,

of course, be employed in a conventional manner to control any otherdesired operating condi- The charging stock, which is a mixture ofnormally gaseous hydrocarbons consisting principally of propenes,butenes and the'corresponding paraflins, is supplied to the system at atemperature of approximately 100 F. from a debutanizer operated inconjunction with a cracking system, not illustrated. A controlledquantity of the total gaseous charging stock is passed through heatexchanger 4 and therein preheated to a temperature of approximately 425F. This temperature and quantity will be varied, during the operation,with variations in the temperature and/or quantity of the heatedproducts leaving the reaction zone. The remaining portion of thecharging stock is passed through heat exchanger 8 in indircetheatexchange with steam and therein preheated toa temperature ofapproximately 308 F. This temperature and quantity will also vary withchanges in the temperature and/or quantity of, the total charging stockas well as with changes in the temperature and/or quantity of the otherpreheated stream of charging stock, but the temperatures and relativequantities of these two preheated streams are so regulated that, whencommingled in line 6 at'a superatmosphere pressure of approximately 1000pounds per square inch, the temperature of the commingled streams isapproximately400 F. The reaction products leave the catalytic reactionzone at a varying temperature of theorder of 450 F. and asuperatmospheric' pressure of about 950 pounds per square inch. They arecooled in heat exchanger 4 by indirect heat exchange'with that portionof the charging stock supplied through this zone and the pressure isreduced as the conversion products pass through valve IS in line I8 toapproximately 100 pounds per square inch, which pressure is employedinstabilizer 20. The resulting temperature of the w changer 6. on theother hand, when the quanconversion products entering the stabilizer iscontrolled to remain substantially constant at approximately 200 F. I

When, for example, the temperature of the charging stock supplied to thesystem from the debutanizer decreases and/or when the quantity of totalcharging stock supplied to the system increases, the temperature in line[2 will begin to decrease and controller 21 functions to increase thesupply of heating medium to heat extity of total charging stock suppliedto the system decreases and/or when its temperature increases,controller 21 will function to decrease the quantity of steam suppliedto heat exchanger 6. When either of these variations involvesa change inthe total quantity of charging stock supplied to the system and/or whenthe quantity of polymerizable olefins supplied to the system varies, itwill be reflected in an increased or de; creased temperature of thestream of hot conversion products supplied to heat exchanger 4.

When this happens controller 28 will function to accordinglylincrease ordecrease the proportion of the total charging stock supplied to heatexchanger 8 and then -maintain the temperature of the conversionproducts entering stabilizer 28 substantially constant. Controller 21will then compensate for the change in the quantity of charging. stocksupplied to heat exchanger ,4.

As another example of a change in operating conditions which may occurand require compensation, the activity of the catalyst will graduallydecreaseduring' prolonged operation of the catalyst bed and result in adecreased temperature of the reaction products supplied to heatexchanger 4. When this occurs, the decreased temperature in the streamof conversion products entering stabilizer 28 will cause controller 28to restrict the opening through valve 3, thereby decreasing the flow ofcharging stock through heat exchanger 4 and increasing its flow throughheat exchanger 6. This will result in a momentary temperature decreasein line I2, causing controller 21 to open valve 8 and increase the flowof heating medium through heat exchanger 6. In this manner the desiredtemperatures are re established in lines [2 and I8 I claim as myinvention:

1. A method of maintaining asubstantially constant temperature in astream of reactants entering a reaction zone and maintaining anindependent, substantially constant temperature in a stream of reactionproducts discharged from said zone, which comprises passing a portion ofsaid reactants in indirect heat exchange with said reaction products,passing the remaining portion of said reactants in indirect heatexchange with a separate heating medium, commingling the streams ofreactants discharged from said heat exchange steps, supplying thecommingled stream to the reaction zone, controlling the quantity of thefirst named portion in response to the temperature of the reactionproducts discharged from the first mentioned heat exchange step, andcontrolling the heat supplied to said remaining portion in the secondheat exchange step in response to the temperature of saidcommingledstream of reactants being supplied to the reaction zone; v

2. A method of maintaining a substantially constant temperature in astream of reactants entering a reaction zone and maintaining anindependent, substatially constant temperature in a stream of reactionproducts discharged from said zone which comprises, passing a portion ofsaid reactants in indirect heat exchange with said reaction products,passing the remaining portion of said reactants in indirect heatexchange with a separate heating medium, varyingthe quantity of thefirst named portion in accordance with variations in the temperature ofthe stream of; reaction products discharged from the first mentionedheat exchange step, and

varying the heat supplied to said remaining portion in the. second heatexchange stepv in accordance with variations in the temperature of saidcommingled stream of reactants being supplied to the reaction zone. I v

3. A method of maintaining a substantially constant temperature in astream of reactants entering a reaction zone and maintaining anindependent, substantially constant temperature in a' stream of reactionproducts discharged from said zone which comprises, passing a portion ofsaid reactants in indirect heat exchange with relation to variations inthe temperature of said commingled stream of reactants supplied to thereaction zone.

-4. A method of maintaining a substantially constant temperature in; astream of reactants entering a reaction zone and'maintaining anindependent, substantially constant temperature in a stream of reactionproducts discharged from said zone which comprises, passing 'a portion01' said reactants in indirect heat exchange with said reactionproducts, passing the remaining portion of said reactants in indirectheat exchange with a separate heating medium, controlling the' quantityof said first named portion in response to the temperature ofthe'conversion products discharged from the first named heat exchangestep, and controlling the quantity said reactants in indirect heatexchange with said reaction products, passing the remaining portion ofsaid reactants in indirect heat exchange with a separate heating medium,varying the quantity of said first named portion in cordance withvariations in the temperature of accordance with variations in thetemperature of the reaction productsdischarged from the first named heatexchange step, and varying the quantity at said'separate heating mediumsupplied to the second heat exchange step .in acthe commingled stream ofreactants being supplied to the reaction zone.

6. A method of maintaining a substantially constant temperature'in astream of reactants entering a reaction zone and maintaining an in--dependent, substantially constant temperature in a stream of reactionproducts discharged from Y 'said zone which comprises, passing a portionof said reactants in indirect heat exchange with 'said reactionproducts, passing the remaining portion of. 'said reactants in indirectheat exchange with a separate heating medium, varying the quantity ofthe first named portion in direct relation'to variations in thetemperature of the reaction products discharged from the first mentionedheat exchange step, and varying the quantity of saidseparate heatingmedium supplied to the second mentioned heat exchange step in inverserelation to variations in the temperature of the commingled stream ofreactants being supplied to the reaction zone.

7. In a processwherei'n charging stock comprising olefinic hydrocarbonsis subjected to poly--' merization to convert the samejnto substantialyields "of desirable polymers, the method of temperature control whichcomprises, passing in indirect heat exchange with hot conversionproducts tion a portion of said charging stock, the quantity of which isregulated to coolsaid conversion products to a predeterminedsubstantially constant temperature, passing the remaining portion oi.the charging stock in indirect heat exchange with a separate heatingmedium, commingling the resultant heated charging stock from both heatexchange steps, supplying the commingled stream to the zone of saidpolymerization, and controlling the quantity oi. heat supplied to thatportion of the charging stock passed through the second mentioned heatexchange step to give a predetermined substantially constant temperaturein said commingled streamn chargedfrom the zone of said polymeriza 8. Ina process for the catalytic polymerization .of temperature control'whichcomprises, efl'ecting a portion of said controlled cooling of theconversion products b'y 'materially reducing the pressure in the zone ofsaid separation relative to that )employed in the reaction zone,effecting the remaining portion of said controlled cooling of theconversion products by passing the same in indirect heat exchange with aportion of said stream of charging stock, controlling the quantity ofsaid charging stock supplied to said heat exchange step in response tothe temperature of the stream of said conversion products subsequent toboth of the cooling steps, passing the remaining portion of said streamof charging stock in indirect heat exchange with a separate heatingmedium, commingling the thus separately heated portions of the chargingstock, supplying the resulting commingled stream of charging stock tothereaction zone, and controlling the quantity of heat supplied to thecharging stock'in the second heat exchange step in response to thetemperature of said commingled str am.

9. An apparatus of the means for supplying reactants thereto, means fordischarging reaction products therefrom, means including two heatexchange zones for heating said reactants prior to their introductioninto said reaction zone, meansfor supplying a separate portion of saidreactants to each of the heat exchange zones, means for commingling theheated reactants from eachof said heat exchange zones and supplying thecommingled.

stream to the reaction zone, means for passing the hot conversionproducts discharged from said reaction zone through one of said heatexchange I zones, means for passing a separate heating medium throughthe other heat exchange zone, means, responsive to the temperature ofthe conversion products dischargedfrom the heat exchange zone to whichsaid hot conversion prod ucts are supplied, for controlling the quantityof said reactants supplied to the same heat exchanger zone and means,responsive to the temperature of said commingled stream of heatedreactants, for controlling the temperature to which that portion of said.reactants supplied to the other heat exchange step is heated therein.

l0. An apparatus of the character described racter described comprising,in combination, a reaction zone,

comprising, in combination, a zone of indirect heat exchange, means forpassing a portion of a stream of charging stock therethrough, a separatezone of indirect heat exchange, means for passing the remainingportion-oi said stream of charging stock therethrough -meansfor/commingling said portions oi the charging stock passed through thetwo heat exchange zones,.a

reaction zone, means for supplying the commingled stream of chargingstock to the reaction zone, means for effecting conversion of saidreactants in the' reaction zone at elevated temperature and substantialsuperatmospheric pressure,

means for dischargingresultant hot conversion products from'the reactionzoneand passing the same as a heating medium through the first mentionedzone of indirect heat exchange, means for discharging resultantpartially cooled conversion products irom the first named heat exchangezone substantially reducing the pressure imposed thereon and thereafterseparating the same into the desired components, means for sponsive tothe temperature of said conversion products following said pressurereduction for controlling the quantity of reactants supplied to thefirst named heat exchange zone and means responsive to the temperatureof said commingled stream of reactants for controlling the heat suppliedto the reactants by said separate heating medium in the second mentionedheat exchange zone.

JOSEPH E. WESTENBERG.

